Abstract: The geographical patterns and differentiation of species diversity of seed plants in Tibet were investigated based on large-scale plant distribution information through combination with geographic information system and statistical analysis. The results showed that the discreteness of datasets of plant diversity and flora differentiation decreased from species to families. Compared with that of families, the spatial variability of species and genus was more apparent, which may be because that species, genus and families represent different periods of geological history. Compared with central and northern regions, the southern Tibet with more complex topography, especially the east southern Tibet, had more diverse plants whether on the species or genus level. There was a significant positive correlation between the flora differentiation of seed plants and altitudinal variation, indicating that complex topography might be beneficial for flora differentiation. The flora differentiation had obvious influence on the geographical distribution of plants in the researched area. This may be related to the climate change caused by differential uplift of stratums in the geological history of Tibet.